When an optical semiconductor device constituting an optical interface is flip-chip mounted on a surface of a substrate which a module having the optical interface and electronic components are combined, optical input and optical output is provided in a direction perpendicular to the surface of the substrate at the input/output ends of the optical semiconductor device which may be a surface emitting device, such as, typically, a surface emission laser or photo-detector, or which may be a surface photoreceptor. An optical fiber for guiding an optical signal is required to be laid such that the axis thereof will be in parallel with the surface of the substrate because of requirements including apparatus specifications. A mismatch therefore arises between the direction of optical input and output at the input/output ends of the optical semiconductor device and the installation direction required of the optical fiber.
As a first method in resolving such a situation, for example, a method proposes as disclosed in Patent Document 1, that a light-receiving section and a light-emitting section of an optical semiconductor device constituting an optical interface disposed on a substrate are connected with connecting ends of the optical fibers through connectors constituted by a receptacle and a plug, for example.
According to such a method, as shown in FIG. 23, optical signals are input and output at a light-receiving section 2R and a light-emitting section 2P of an optical semiconductor device 2 disposed on a substrate 1, respectively, along a direction that is perpendicular to a surface of the substrate 1 as indicated by the arrows. Connecting ends of an optical fiber 3 connected to the light-receiving section 2R and an optical fiber 4 connected to the light-emitting section 2P, respectively, are connected with the fibers at parts thereof located upstream or downstream of the connecting ends being bent at about 90 degrees such that the connecting ends become perpendicular to the surface of the substrate.
As a second method, a method is proposed as disclosed in Patent Documents 2 and 3, in which end faces of optical fibers facing a light-receiving section and a light-emitting section of an optical semiconductor device, respectively, are processed to provide them with a 45 degrees reflector (reflection surface). In this case, as shown in FIG. 24, optical fibers 5 and 6 are disposed such that their axes are in parallel with a surface of a substrate 1 on which an optical semiconductor device 2 as described above is disposed. 45 degrees reflectors 5a and 6a are provided on end faces of the optical fibers 5 and 6 which are opposite to light-receiving section 2R and light-emitting section 2P of the optical semiconductor device 2, respectively. As a result, a light beam guided by the optical fiber 5 along the direction indicated by the arrow is refracted by the 45 degrees reflector 5a at 90 degrees to be input to the light-receiving section 2R.
As a third method, a system as disclosed in Non-Patent Document 1 has been standardized as a de facto standard, according to which an optical semiconductor device is provided on a substrate vertically secured in a position facing a connecting end of an optical fiber such that the substrate intersects the axis of the optical fiber to allow the optical fiber to be laid on a horizontal surface of the substrate.    Patent Document 1: Japanese Patent No. 3,511,479    Patent Document 2: Japanese Patent No. 3,532,456    Patent Document 3: Japanese Patent No. 3,150,070    Non-Patent Document 1: “Appendix to SNAP12 Multi-Source Agreement: Rev. 1.1, May 15, 2002